Aluminum base alloy



Fa'lentecl giant 2, l'ldil midget ALill /lEilNlJli i William E.Mansfield,

No Drawing.

BASE AKLQY Garfield Heights, Qhio Application November 16, 1936,

Serial No. llLdliS My invention relates to aluminum base alloys and moreparticularly to aluminum base alloys containing a substantial amount ofiron.

In preparing castings from aluminum base 5 alloys by casting inpermanent or semi-permanent molds, or in die castings, considerabledifficulty is experienced in obtaining satisfactory castings with alloysoi high iron content. Iron occurs as a normal impurity in primaryaluminum in amounts ranging up to 25% to .5% and is usually present inconsiderably larger quantities in secondary aluminum.

Furthermore, when the alloys are mixed in iron pots and cast inpermanent or semi-permanent molds, the amount of iron dissolved in thealuminum from the melting and casting equipment is often considerable.When iron is present in more than small amounts in many alloys utilizedfor making castings, however, it lowers the strength and ductility ofthe alloy and adversely affects it's casting properties. Castings havinga high iron content which have been prepared from most aluminum alloysare consequently inferior to castings prepared from similar alloyshaving at the desired minimum iron content, both with respect to finishand to physical properties.

Patent No. 1,997,494 granted to me on April 9, 19-35, discloses the useof antimony to counteract the deleterious effects of the iron inaluminum alloys. As disclosed in that patent, the antimony serves tobreak up the large crystalline structure caused by the high ironcontent. The antimony also reduces the shrinkage of the alloy duringsolidification and increases the elongation and reduces the brittlenessof the cast alloy. Furthermore, the antimony increases the corrosiveresisting properties and lowers the thermal coeificient of expansionwhich renders such alloys very desirable for use in castings, such aspistons, where a low thermal coeficient of expansion is desirable.

I have made the discovery that if a metal of the tungsten group, such astungsten, molybdenum or uranium, or a metal of the vanadium group, suchas vanadium, cclumblan or tantalum, or a metal, such as beryllium, boronor zirconium, or a mixture, compound or alloy of two or more of suchmetals, is added to aluminum base alloys containing iron and antimony,an alloy will be produced that has a denser grain structure and bettercasting and machining properties than previous aluminum base alloys ofthis type, and this is especially true with respect to alloys which areseriously afifected by the presence of more than a small amount of iron,such as aluminum base alloys containing nickel, copper, silicon, or twoor more of such metals.

My improved alloy is especially suitable for use in preparing castingsrequiring a dense grain structure, such as pistons, cylinder heads, andthe like, in which iron, silicon and. antimony are present. In suchalloys when both silicon and antimony are present, the silicon or theantimony appears to be precipitated out of solution and this isparticularly true when the silicon is present in amounts greater than3%. The addition of a special alloying ingredient of the type specifled,however, counteracts this tendency and higher amounts of silicon maytherefore be employed. Titanium, chromium and manganese also aid in thisrespect. For instance, titanium or chromium may be present in efiectiveamounts up to 3% but is preferably maintained within a range of .05% to1.5%. Manganese may also be present in amounts ranging up to 3%. Largeamounts of manganese, however, cause the alloy to become brittle. Itwill be understood, however, that I do not desire to be limited to analloy containing silicon because aluminum base alloys containingantimony have a low thermal coemcient of expansion and one or more ofthe special alloying ingredients will effect an improvement in suchalloys, even though silicon is present in amounts less than 3% or ispresent in only such amounts that it may be considered an impurity.

My invention also contemplates the addition of one or more of thespecial alloying ingredients mentioned to aluminum base alloys whichcontain antimony and only the usual amount of iron. For instance, it maybe employed with aluminum alloys containing virgin aluminum andantimony.

It is therefore an object of my invention to provide an aluminum basealloy containing iron and antimony in substantial amounts and a. specialalloying ingredient in an amount sufficient to diminish the deleteriousefiect of the iron so that an alloy will be produced having good castingproperties, even when the amount of iron is relatively high.

Another object of my invention is to provide an aluminum base alloycontaining antimony and a special alloying ingredient which alloy may becast in sand, permanent molds or in dies and from which good castings orforgings may be produced.

A further object of my invention is to provide an aluminum base alloycontaining a substantial amount of silicon and copper, together with aspecial alloying ingredient which 'serves to improve the castingproperties of the alloy.

Another object of my invention is to provide an aluminum base alloycontaining a substantial amount of iron, antimony and an additionalmetal which alloy is particularly adapted to be cast in a permanent moldor from which die and sand castings may be made.

A still further object of my invention is to provide an improved castinghaving a dense grain structure and a low thermal coeflicient ofexpansion which is formed of an aluminum ,base alloy containingsubstantial amounts of iron.

In practicing my invention, a metal of the tungsten or vanadium groups,beryllium, boron, zirconium, or a mixture, compound or alloy of two ormore of such metals, is added in amounts ranging from effective amountsup to 3% to an aluminum base alloy containing at least 75% aluminum,.05% to 15% antimony, and from 1.5% to 10% of iron.

The amount of aluminum, however, may range from 75% to 95% and ispreferably maintained above The amount of the special alloying metal oringredient which is added to the aluminum base alloy is dependent uponthe iron and antimony content. For instance, if the aluminum utilizedcontains more than 2% of iron, say from 3% to 10%, and antimony ispresent in an amount suificient to counteract the deleterious effect ofthe high iron content, more of the special alloying metal will berequired than when the iron is below 3%. In preparing castings fromsecondary alloys, I prefer to utilize from approximately .05% to 3% ofthe special alloying ingredient.

The amount of antimony which is present is also dependent upon theamount of iron. Thus, for aluminum alloys containing more than 2% iron,say from 2% to 10%, the amount of antimony will be relatively high, sayfrom .5% to 7%. The amount of antimony, which is added to the castingalloy, however, will not usually exceed 7%, and the preferred amountranges from .l% to 4%.

In addition to iron, antimony and the special alloying ingredient, myimproved alloy may also contain copper or nickel, or a mixture of copperand nickel, in an amount ranging from 2% to 12%. Silicon may also bepresent in an amount ranging from more than incidental impurities up to10%, either alone or in combination with copper or nickel, or a mixtureof copper and nickel.

In preparing castings, the amount of magnesium, lead and tin should bemaintained below .5%, respectively, and the amount of zinc should bebelow 3% and preferably below 2%. Magnesium in large amounts has a verypronounced,

efiect upon the hot shortness of aluminum alloys; a property which isvery deleterious in producing alloys in permanent or semi-permanentmolds or by the die casting process. The magnesium also increases thehardness, which decreases the machinability and causes excessivebreakage in trimming. In producing castings in dies, it is thereforeessential that the amount of magnesium which is present should bemaintained below .5% and preferably below 25%.

In castings requiring special hardness, it -is advantageous, however, tohave some magnesium present, say from approximately .1% to .35%.

My invention is especially adapted for use in castings which have a lowthermal coefficient of expansion, such as pistons, cylinder heads andthe like. In providing an alloy for preparing such castings, silicon isusually added to lower the thermal coefficient of expansion. whensecondary aluminum alloys are utilized for such a purpose, however, andthe amount of silicon is comparatively high, the results have not beenentirely satisfactory even though antimony is added to the alloy tocounteract the deleterious effects of the iron. The reason for thisappears to be that the silicon or antimony is precipitated out ofsolution and although fairly satisfactory results have been obtained,the castings do not have the particularly fine grain structure desired.By adding one or more of the special alloying ingredients mentioned, ortitanium. manganese or chromium to the alloys, or a mixture, compound oralloy of two or more of such metals, I have found that an alloy havingconsiderably improved casting properties is obtained. When two or moreof the special alloying ingredients are added or when one or more ofsuch metals and one or more metals selected from a group consisting ofmanganese, titanium and chromium are'added, they may be introduced intheform of a compound, mixture or alloy. When two or more metalsselected from the group of metals consisting of manganese, titanium andchromium are added, they may be introduced in a similar manner. I havefound that a metal of the tungsten group, or a mixture of two or more ofsuch metals, or a mixture of a metal of the tungsten group and titanium,is especially effective in this respect.

The following specific example will serve to illustrate and explain myinvention although it will be understood that I do not desire to belimited to the specific alloys or to the proportions specified. Analuminum base alloy was prepared containing the following ingredients inapproximately the proportions specified:

Per cent Copper 7 Silicon 4 Iron 3 Antimony 2.5 Magnesium .25 Tungsten.25

Castings were prepared in a permanent mold having a fine grain structureand similar results going example may be varied substantially asfollows:

Per cent Copper 4 to 10 Silicon 3 to 8 Iron 2 to 10 Antimony .5 to 15Tungsten .05 to 1.5

while the magnesium should be maintained below .5% and preferably below25%.

The alloy may be prepared in any desired manner, such as by melting theingredients together and introducing the special alloying ingredientinto molten aluminum, or if other metals are present, the specialalloying ingredient may be alloyed with such metals and introduced intothe molten bath. Another convenient method is to prepare a rich alloy ofthe special alloying ingredient and aluminum and introduce the alloyinto the molten aluminum. I may also add the special alloying ingredientin the presence of or in the form of a fluoride in a manner similar tothat described for the addition of antimony in my former patent to whichreference has been made. The antimony may also be introduced in themanner disclosed in my previous patent.

In specifying the percentage of alloying ingredients in my improvedalloy, it will be understood that the range of percentage given refersto the finished castings as well as to the ingot. In order to producegood castings, it has heretofore been necessary to maintain the amountof iron in the castings below a certain percentage, which is the totalamount in the original alloy as well as that dissolved in the castingoperation. My invention is especially suitable for producing alloys forsand, chill mold or die castings. It is well known that iron has aharmful eifect upon castings as it causes the alloy to become sluggishin the casting operation. and brittle in the finished product. By addingantimony and one or more of the special alloying ingredients specified,however, the deleterious effects of the iron may be minimized orprevented. My improved alloy also has the property of solidifyingquickly which makes it especially desirable for use in preparing chillmold castings.

While the special alloying ingredient, or a mix-'- ture of two or moreof such ingredients, is particularly valuable as an addition to aluminumbase alloys in which secondary aluminum having a high iron content isemployed, it also improves the grain structure of aluminum base alloyscontaining antimony and silicon, in which virgin aluminum containingiron as a normal impurity is utilized. Eor instance, castings may beprepared in which the antimony is present in amounts ranging from .05%to and preferably from .5% to 7% and in which the silicon is present inamounts ranging from effective amounts more than normal impurities up to13% and preferably from 3% to-10%. Such alloys may contain both antimonyandsilicon and this is particularly true v when castings, such aspistons or cylinder heads, are desired having a low coefficient ofexpansion. Copper or nickel, or a combination of copper and nickel, andmagnesium within the ranges specified for alloys of high iron contentare also preferably present in this alloy. When silicon is present inamounts greater than 3% and antimony is also present,titanium',manganese or chromium in amounts ranging from .05% to 3% alsoappear to be eii'ective in maintaining the antimony and silicon insolution and may be utilized in place of one of. the special alloyingingredients or in combination with it.

From the foregoing description of my invention, it will be seen that Ihave provided an improved alloy which counteracts or diminishes thedeleterious effects of iron. I am therefore able to utilize a lowergrade of aluminum in forming castings and this is particularly true inpreparing castings in chill molds in which it has heretofore beennecessary to maintain the amount of 2% and preferably below a maximum of1.25%.

It will also be apparent that I have provided an improved alloy that isparticularly adapted for use in castings in which a low coeflicient ofexpansion is desired, and particularly for use in pistons, cylinderheads, and the like, in which both silicon and antimony are present.

To those skilled in the art, many modifications of and widely differingembodiments and applications of my invention will suggest themselveswithout departing from the spirit and scope thereof. My disclosure andthe description herein are purely illustrative and are not intended tobe in any sense limiting.

What I claim is:

1. An aluminum -antimor'iytungsten group metal alloy having a. linergrain structure, higher tensile strength and better casting propertiesthan an aluminum-antimony alloy of similar composition, said alloyconsisting of antimony in amounts ranging from .05% to 15%, ametal ofthe tungsten group in effective amounts up to 3%, and the remainder ofaluminum and any other metal or metals not subversive of the abovecharacteristics.

2. An aluminum-antimony tungsten group metal alloy having a finer grainstructure, higher tensile strength and better casting properties than analuminum-antimony alloy of similar composi-- tion, said alloy consistingof antimony in amounts ranging from .05% to 15%, a metal of the tungstengroup in effective amounts up to 3%, from 1.5% to 10% iron, and theremainder aluminum and any other metal or metals not subversive of theabove characteristics.

sten g oup in effective amounts up to 3%, iron in amounts ranging from1.5%, to 10%, silicon in effective amounts up to 13%, and the remainderaluminum and any other metal or metals not sub-' versive of the abovecharacteristics.

4. An aluminum-antimony-tungsten group metal alloy having a finer grainstructure, higher tensile strength and better casting properties thanaluminum-antimony alloys of a similar composition, said alloy consistingof .5% to 7% antimony, .5% to 10% iron, 3% to 10% silicon, a metal ofthe tungsten group'in effective amounts up to 3%, and the remaind raluminum and any other metal or metals not subversive of the abovecharacteristics.

5. An aluminum-antimony-tungsten alloy having a finer grain structure, ahigher tensile strength and better casting properties than analuminum-antimony alloy of a similar composition, said alloy consistingof .5% to 7% antimony, 1.5% to 10% iron, .05% to 3% tungsten, and theremainder 'of aluminum and any other metal or metals not subversive ofthe above characteristics.

WILLIAM E. MANSFIELD.

